From mboxrd@z Thu Jan  1 00:00:00 1970
From: keith.busch@intel.com (Keith Busch)
Date: Thu, 30 Jun 2016 10:57:51 -0400
Subject: [PATCHv2 1/3] nvme: Remove RCU namespace protection
In-Reply-To: <20160630064838.GA1608@infradead.org>
References: <1466702946-13065-1-git-send-email-keith.busch@intel.com>
 <1466702946-13065-2-git-send-email-keith.busch@intel.com>
 <20160628083137.GA32618@infradead.org>
 <20160628163512.GB8607@localhost.localdomain>
 <20160630064838.GA1608@infradead.org>
Message-ID: <20160630145750.GC13842@localhost.localdomain>

On Wed, Jun 29, 2016@11:48:38PM -0700, Christoph Hellwig wrote:
> But we remove it from the list before del_gendisk in
> nvme_remove_invalid_namespaces and nvme_scan_ns_list already.  I guess
> that's fine because we're not going to do I/O on them at this point,

Right, we can safely remove them from the list for those other cases
precisely because they can't do IO anymore.

> but what prevents us form doing this two step removal in
> nvme_remove_namespaces?

If the controller fails during del_gendisk, we have to kill all
the request queues and set capacities to 0 to force del_gendisk to
complete. If the namespace isn't in the ctrl->namespace list, the driver
can't find the namespace to kill.